2001 Suburban - Hard Starting When Below 0 F

[mike g 09]

Hello Everyone.

 

First time here - looks like a very fine forum.

 

We have recently purchased a 2001 Chev Suburban LT, with about 114,000 miles on it. It has the 5.3 L engine, which seems to be fine, except for a slight knocking noise when it is cold (first 30 seconds or so after starting).

 

The engine starts well, except for when it is below zero degrees F. I will have the tank or block heater plugged in overnight, so it cranks fine. However, it will take 2-5 tries of cranking it (5-10 seconds per attempt) to get it to fire.

 

I have no idea what is causing it. I have assumed it is the fuel pump, since I can hear the fuel pump operating (slight vibrating noise). After the first time, I turned on the key and waited 5 seconds or so before cranking, my assumption being that the fuel pump needed extra time when cold. This seemed to help a bit.

 

This morning, it was minus 12 F. I made about 3 attempts at cranking it, before I floored the accelerator when cranking. No avail this time.

 

Thoughts?

 

Thanks in advance,